Effect of Camera-Like Aperture in Quest for Maintaining Quasi-Constant Radiation Inside a Solar Reactor

2010 ◽  
Author(s):  
Nesrin Ozalp ◽  
Anthony Toyama ◽  
D. Jaya Krishna ◽  
Reza Rowshan ◽  
Yasser Al-Hamidi
Keyword(s):  
Solar Radiation ◽  
Solar Energy ◽  
Operating Conditions ◽  
Solar Flux ◽  
Process Efficiency ◽  
Distribution Model ◽  
Peak Performance ◽  
Aperture Diameter ◽  
Small Surface ◽  
Solar Reactor

Solar reactors can convert intermittent solar radiation into storable chemical energy in the form of fuels that are transportable. In order to use solar energy as a source of high temperature process heat in a solar reactor, incident radiation needs to be concentrated over a small surface area, the inlet of which is called the aperture. The image of the incoming solar radiation over the aperture can be approximated by a Gaussian distribution where the solar radiation inside the reactor varies by the peak value and aperture size. Due to the transient nature of solar energy, there is a critical need for proper control to maximize system efficiency under field conditions. This paper provides numerically proven advantages of having a camera-like variable aperture, one which is sensitive to natural variations in solar flux, and having the ability to shrink or enlarge accordingly in order to maintain quasi-constant radiation inside the reactor. Our numerical results from optical, thermodynamic, and flow dynamic simulations led us to develop a computational two dimensional heat transfer distribution model inside the reactor in order to validate our optical results. The simulation results show that a changing aperture diameter with respect to a changing incoming solar flux density facilitates keeping quasi-constant and homogenous temperature distributions inside the reactor. Since the temperature has a major impact on reactant to product conversion efficiency, by keeping the temperature constant, process efficiency is kept high. By maintaining the internal temperature despite variable operating conditions the system can maintain peak performance through a wider insolation range than fixed aperture systems.

Effect of Cameralike Aperture in Quest for Maintaining Quasi-Constant Radiation Inside a Solar Reactor

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Nesrin Ozalp ◽  
Anthony Toyama ◽  
Jayakrishna Devanuri ◽  
Reza Rowshan ◽  
Yasser Al-Hamidi
Keyword(s):  
Solar Radiation ◽  
Solar Energy ◽  
Operating Conditions ◽  
Solar Flux ◽  
Process Efficiency ◽  
Distribution Model ◽  
Internal Temperature ◽  
Aperture Diameter ◽  
Small Surface ◽  
Solar Reactor

Solar reactors can convert intermittent solar radiation into storable chemical energy in the form of fuels that are transportable. In order to use solar energy as a source of high temperature process heat in a solar reactor, incident radiation needs to be concentrated over a small surface area, the inlet of which is called the aperture. The image of the incoming solar radiation over the aperture can be approximated by a Gaussian distribution where the solar radiation inside the reactor varies by the peak value and aperture size. Due to the transient nature of solar energy, there is a critical need for proper control to maximize system efficiency under field conditions. The objective of this paper is to present numerically proven advantages of having a camera-like variable aperture, one that is sensitive to natural variations in solar flux, and having the ability to shrink or enlarge accordingly in order to maintain quasi-constant radiation inside the reactor. Since the internal temperature has a major impact on reactant to product conversion efficiency, by maintaining the temperature constant, process efficiency is kept high. By maintaining the internal temperature despite transient operating conditions, the system can maintain peak performance through a wider insolation range than fixed aperture systems. Our numerical results from optical, thermodynamic, and flow dynamic simulations led us to develop a computational two dimensional heat transfer distribution model inside the reactor in order to validate our optical results. The combined simulation results show that correctly varying the aperture diameter with respect to transient incoming solar flux densities facilitates the maintenance of quasi-constant temperature distributions inside the reactor.

Analysis of Catalytically Enhanced Solar Absorption Chemical Reactors: Part II—Predicted Characteristics of a 100 kWchemical Reactor

1992 ◽  
Vol 114 (2) ◽  
pp. 112-118 ◽  
Author(s):  
R. D. Skocypec ◽  
R. E. Hogan
Keyword(s):  
Solar Energy ◽  
Convective Heat Transfer Coefficient ◽  
Fluid Phase ◽  
Operating Conditions ◽  
Solar Flux ◽  
Heterogeneous Reactions ◽  
Catalyst Loading ◽  
Reactor Performance ◽  
Solar Absorption ◽  
Concentrated Solar Energy

The CAtalytically Enhanced Solar Absorption Receiver (CAESAR) is a 100 kWchemecal test reactor currently in operation. This type of high-temperature chemical reactor volumetrically absorbs concentrated solar energy throughout a catalytic porous absorber matrix volume, promoting heterogeneous reactions with fluid-phase reactant species flowing through the absorber. A numerical model of these reactors has been developed to provide guidance in the catalytic matrix design for CAESAR. In the CAESAR reactor, methane is reformed using carbon dioxide and a rhodium catalyst. In addition, the model is being used to evaluate both the reactor performance and test data. This paper presents the thermal and chemical characteristics of the reactor for varying incident solar flux, fluid mass flow, convective heat-transfer coefficient, solar and infrared extinction coefficients, and catalyst loading. Predicted CAESAR performance is based on a prototype absorber and anticipated operating conditions. Model results suggest the mass flux must be proportioned to the incident solar flux radial distribution to prevent unacceptably high local temperatures and to provide a reactor having more uniform exit conditions. Either the catalytic loading or geometric thickness of the absorber should be increased for conversion to approach equilibrium levels. Also, the optical density of the matrix (particularly at the sunlit side of the reactor) should be decreased to distribute solar energy more uniformly in depth and decrease matrix temperatures at the front of the absorber.

Thermochemical Conversion of Biomass Using Solar Energy: Use of Nanoparticle-Laden Molten Salt as the Working Fluid

2009 ◽  
Author(s):  
Himanshu Tyagi ◽  
Patrick E. Phelan ◽  
Ravi S. Prasher
Keyword(s):  
Solar Radiation ◽  
Solar Energy ◽  
Molten Salt ◽  
Concentration Factor ◽  
Solar Collector ◽  
Energy Use ◽  
Operating Conditions ◽  
Thermochemical Conversion ◽  
Working Fluid ◽  
Fluid Mixture

Solar energy can potentially be used to convert biomass into more readily usable fuel. The use of solar energy in such a process improves the overall conversion efficiency of the system significantly by eliminating combustion of a portion of biomass needed to heat the rest of it to a temperature where pyrolysis occurs. The present study models the thermochemical conversion process during pyrolysis of biomass matter into product gases. Concentrated solar radiation is used as the source of heating of the biomass. The biomass is indirectly heated by a mixture of molten salts (Na2CO3 and K2CO3) and nanoparticles (copper), which acts as the absorbing medium and in turn heats the biomass matter (cellulose). A two-stage heat transfer and chemical reaction analysis is carried out in order to simulate the simplified operating conditions of a solar-powered gasifier. The temperature of the molten salt at the exit of the reactor is held fixed at 1000 K (727°C). The calculations are carried out at different values of solar concentration factor ranging from 10 to 60. The results show that the temperature of the molten salt mixture at the exit of the solar collector increases with an increase in the solar concentration factor. Moreover the temperature inside the biomass reactor is a function of the concentration factor as well and largely the determining factor of the rate of biomass conversion into product gases. At the highest concentration factor (Cf = 60), the model predicts that the reactor is able to convert 1.1 tons of biomass into product gases each hour using 900 kW of solar radiation at an overall efficiency of 8%. The main finding of this study is that under similar operating conditions a solar collector using a direct absorption fluid (mixture of nanoparticles and molten salt) would require significantly less concentration factor (an order of magnitude reduction) than a conventional solar collector. A conventional solar collector is defined as one where the solar radiation heats up a solid surface (such as tube walls) which in turn heats up the working fluid (molten salt). Such a reduction in concentration factor would translate into lower concentrator area, and consequently lower initial capital cost.

scholarly journals Solar Carbo-Thermal and Methano-Thermal Reduction of MgO and ZnO for Metallic Powder and Syngas Production by Green Extractive Metallurgy

Processes ◽  
2022 ◽  
Vol 10 (1) ◽  
pp. 154
Author(s):  
Srirat Chuayboon ◽  
Stéphane Abanades
Keyword(s):  
Solar Energy ◽  
Total Pressure ◽  
Extractive Metallurgy ◽  
Thermal Reduction ◽  
Operating Conditions ◽  
Equilibrium Analysis ◽  
Metallurgical Process ◽  
Solid Carbon ◽  
Solar Reactor ◽  
Reaction Extent

The solar carbo-thermal and methano-thermal reduction of both MgO and ZnO were performed in a flexible solar reactor operated at low pressure through both batch and continuous operations. The pyro-metallurgical process is an attractive sustainable pathway to convert and store concentrated solar energy into high-value metal commodities and fuels. Substituting fossil fuel combustion with solar energy when providing high-temperature process heat is a relevant option for green extractive metallurgy. In this study, a thermodynamic equilibrium analysis was first performed to compare the thermochemical reduction of MgO and ZnO with solid carbon or gaseous methane, and to determine the product distribution as a function of the operating conditions. The carbo-thermal and methano-thermal reduction of the MgO and ZnO volatile oxides was then experimentally assessed and compared using a directly irradiated cavity-type solar reactor under different operating conditions, varying the type of carbon-based reducing agent (either solid carbon or methane), temperature (in the range 765–1167 °C for ZnO and 991–1550 °C for MgO), total pressure (including both reduced 0.10–0.15 bar and atmospheric ~0.90 bar pressures), and processing mode (batch and continuous operations). The carbo-thermal and methano-thermal reduction reactions yielded gaseous metal species (Mg and Zn) which were recovered at the reactor outlet as fine and reactive metal powders. Reducing the total pressure favored the conversion of both MgO and ZnO and increased the yields of Mg and Zn. However, a decrease in the total pressure also promoted CO2 production because of a shortened gas residence time, especially in the case of ZnO reduction, whereas CO2 formation was negligible in the case of MgO reduction, whatever the conditions. Continuous reactant co-feeding (corresponding to the mixture of metal oxide and carbon or methane) was also performed during the solar reactor operation, revealing an increase in both gas production yields and reaction extent while increasing the reactant feeding rate. The type of carbon reducer influenced the reaction extent, since a higher conversion of both MgO and ZnO was reached when using carbon with a highly available specific surface area for the reactions. The continuous solar process yielded high-purity magnesium and zinc content in the solar-produced metallic powders, thus confirming the reliability, flexibility, and robustness of the solar reactor and demonstrating a promising solar metallurgical process for the clean conversion of both metal oxides and concentrated solar light to value-added chemicals.

scholarly journals Detrended Multiple Cross-Correlation Coefficient applied to solar radiation, air temperature and relative humidity

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Andrea de Almeida Brito ◽  
Heráclio Alves de Araújo ◽  
Gilney Figueira Zebende
Keyword(s):  
Relative Humidity ◽  
Solar Radiation ◽  
Solar Energy ◽  
Correlation Coefficient ◽  
Air Temperature ◽  
Cross Correlation ◽  
Global Solar Radiation ◽  
Meteorological Variables ◽  
Hourly Data ◽  
Cross Correlations

AbstractDue to the importance of generating energy sustainably, with the Sun being a large solar power plant for the Earth, we study the cross-correlations between the main meteorological variables (global solar radiation, air temperature, and relative air humidity) from a global cross-correlation perspective to efficiently capture solar energy. This is done initially between pairs of these variables, with the Detrended Cross-Correlation Coefficient, ρDCCA, and subsequently with the recently developed Multiple Detrended Cross-Correlation Coefficient, $${\boldsymbol{DM}}{{\boldsymbol{C}}}_{{\bf{x}}}^{{\bf{2}}}$$DMCx2. We use the hourly data from three meteorological stations of the Brazilian Institute of Meteorology located in the state of Bahia (Brazil). Initially, with the original data, we set up a color map for each variable to show the time dynamics. After, ρDCCA was calculated, thus obtaining a positive value between the global solar radiation and air temperature, and a negative value between the global solar radiation and air relative humidity, for all time scales. Finally, for the first time, was applied $${\boldsymbol{DM}}{{\boldsymbol{C}}}_{{\bf{x}}}^{{\bf{2}}}$$DMCx2 to analyze cross-correlations between three meteorological variables at the same time. On taking the global radiation as the dependent variable, and assuming that $${\boldsymbol{DM}}{{\boldsymbol{C}}}_{{\bf{x}}}^{{\bf{2}}}={\bf{1}}$$DMCx2=1 (which varies from 0 to 1) is the ideal value for the capture of solar energy, our analysis finds some patterns (differences) involving these meteorological stations with a high intensity of annual solar radiation.

scholarly journals Tanning Wastewater Treatment by Ultrafiltration: Process Efficiency and Fouling Behavior

Membranes ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 461
Author(s):  
Fu Yang ◽  
Zhengkun Huang ◽  
Jun Huang ◽  
Chongde Wu ◽  
Rongqing Zhou ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Shear Rate ◽  
Membrane Surface ◽  
Filtration Efficiency ◽  
Operating Conditions ◽  
Process Efficiency ◽  
Transmembrane Pressure ◽  
Leather Industry ◽  
Pore Blocking ◽  
The Impact

Ultrafiltration is a promising, environment-friendly alternative to the current physicochemical-based tannery wastewater treatment. In this work, ultrafiltration was employed to treat the tanning wastewater as an upstream process of the Zero Liquid Discharge (ZLD) system in the leather industry. The filtration efficiency and fouling behaviors were analyzed to assess the impact of membrane material and operating conditions (shear rate on the membrane surface and transmembrane pressure). The models of resistance-in-series, fouling propensity, and pore blocking were used to provide a comprehensive analysis of such a process. The results show that the process efficiency is strongly dependent on the operating conditions, while the membranes of either PES or PVDF showed similar filtration performance and fouling behavior. Reversible resistance was the main obstacle for such process. Cake formation was the main pore blocking mechanism during such process, which was independent on the operating conditions and membrane materials. The increase in shear rate significantly increased the steady-state permeation flux, thus, the filtration efficiency was improved, which resulted from both the reduction in reversible resistance and the slow-down of fouling layer accumulate rate. This is the first time that the fouling behaviors of tanning wastewater ultrafiltration were comprehensively evaluated, thus providing crucial guidance for further scientific investigation and industrial application.

scholarly journals A Comparative Study on Fault Detection Methods for Gas Turbine Combustion Systems

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 389
Author(s):  
Jinfu Liu ◽  
Zhenhua Long ◽  
Mingliang Bai ◽  
Linhai Zhu ◽  
Daren Yu
Keyword(s):  
Fault Detection ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Operating Conditions ◽  
Detection Methods ◽  
Distribution Model ◽  
Outlet Temperature ◽  
Combustion System ◽  
Comparison Results ◽  
Gas Turbine Combustion

As one of the core components of gas turbines, the combustion system operates in a high-temperature and high-pressure adverse environment, which makes it extremely prone to faults and catastrophic accidents. Therefore, it is necessary to monitor the combustion system to detect in a timely way whether its performance has deteriorated, to improve the safety and economy of gas turbine operation. However, the combustor outlet temperature is so high that conventional sensors cannot work in such a harsh environment for a long time. In practical application, temperature thermocouples distributed at the turbine outlet are used to monitor the exhaust gas temperature (EGT) to indirectly monitor the performance of the combustion system, but, the EGT is not only affected by faults but also influenced by many interference factors, such as ambient conditions, operating conditions, rotation and mixing of uneven hot gas, performance degradation of compressor, etc., which will reduce the sensitivity and reliability of fault detection. For this reason, many scholars have devoted themselves to the research of combustion system fault detection and proposed many excellent methods. However, few studies have compared these methods. This paper will introduce the main methods of combustion system fault detection and select current mainstream methods for analysis. And a circumferential temperature distribution model of gas turbine is established to simulate the EGT profile when a fault is coupled with interference factors, then use the simulation data to compare the detection results of selected methods. Besides, the comparison results are verified by the actual operation data of a gas turbine. Finally, through comparative research and mechanism analysis, the study points out a more suitable method for gas turbine combustion system fault detection and proposes possible development directions.

scholarly journals The role of L/W in the solar radiation for Saharian cities

2019 ◽  
Vol 91 ◽  
pp. 05006
Author(s):  
Rami Qaoud ◽  
Alkama Djamal
Keyword(s):  
Solar Radiation ◽  
Solar Energy ◽  
Energy Levels ◽  
Direct Solar Radiation ◽  
Test Field ◽  
Natural Lighting ◽  
The Difference ◽  
The Impact ◽  
The Relationship

The urban fabric of the desert cities is based on the principle of reducing the impact of urban canyons on direct solar radiation. Here comes this research, which is based on a comparative study of the periods of direct solarisation and values of the solar energy of urban canyons via two urban fabrics that have different building densities, where the ratio between L/W is different. In order to obtain the real values of the solar energy (thermal, lighting), the test field was examined every two hours, each three consecutive days. The measurement stations are positioned by the three types of the relationship between L/W, (L≥2w, L=w, L≤0.5w). According to the results, we noticed and recorded the difference in the periods of direct solarization between the types of urban engineering canyons, reaching 6 hours a day, the difference in thermal values of air, reaching 4 °C, and the difference in periods of direct natural lighting, reaching 6 hours. It should be noted that the role of the relationship between L/W is to protect the urban canyons by reducing the impact of direct solar radiation on urban canyons, providing longer hours of shading, and reducing solar energy levels (thermal, lighting) at the urban canyons. This research is classified under the research axis (the studies of external spaces in the urban environment according to the bioclimatic approach and geographic approach). But this research aims to focus on the tracking and studying the distribution of the solar radiation - thermal radiation and lighting radiation - in different types of street canyons by comparing the study of the direct solarization periods of each type and the quantity of solar energy collected during the solarization periods.

Evaluation of the Hourly Global Solar Radiation on a Horizontal Plane for Two Sites in Algeria

2014 ◽  
Vol 925 ◽  
pp. 641-645 ◽  
Author(s):  
Mohamed Salmi ◽  
Hassen Bouzgou ◽  
Yarub Al-Douri ◽  
Abdelhakim Boursas
Keyword(s):  
Solar Radiation ◽  
Gaussian Distribution ◽  
Horizontal Plane ◽  
Experimental Validation ◽  
Global Solar Radiation ◽  
Distribution Model ◽  
Experimental Assessment ◽  
Precise Prediction ◽  
Gaussian Distribution Model ◽  
Modelling Approach

We present three models for the estimation of hourly global solar radiation for two sites in Algeria, namely: Djelfa (Latitude 34.68°N, Longitude 3.25°E, Altitude 1126 (m)) and Ain Bessem (Latitude 36.31°N, Longitude 3.67°E, Altitude 629 (m)). The models are: the Gaussian distribution model, the model by Collares-Pereira-RabI and the H.A. model (Hourly absolute modelling approach). The experimental assessment was done using recorded values of the hourly global solar radiation on a horizontal plane during the period 2000-2004. The obtained results show a close similarity between the solar radiation values calculated by the three models and the measured values, especially for the first model. The experimental validation shows promising results for the estimation and precise prediction of the hourly global solar radiation.

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